| The dielectric recovery property of SF6 high voltage circuit breaker is the basis for judging the breaking performance. The numerical simulation of dielectric recovery property involves the numerical calculation of the output characteristics of the hydrodynamic actuator and the numerical simulation of electric field and gas flow field of arc quenching chamber of SF6 circuit breaker. The focal point of the thesis is to investigate of the application of the multi-grid method in the electric field calculation and the numerical simulation of gas flow field of arc quenching chamber.Numerical calculation of electric fieldFor the sack of making the application of multi-grid method easily and making the boundary of complex structure chamber well fitted, the partition body fitting grid generating technique has been investigated, so that the body fitting grids and rectangle grids are generated in each subregion of physic plane and calculating plane respectively, which makes the electric field calculation and the numerical simulation of gas flow field be able to run in same calculation plane.Through the coordinate transformation, the mathematical model for describing electric field distribution and its discrete scheme on the calculation plane are deduced, and the multi-grid method is combined with the discrete scheme and a combination of Finite Difference + Multi-grid Method has been developed.Considering the fact that the finite analytic method possesses the advantage of high precision at the rectangle calculating element, In this thesis, the conventional finite analytic method has been improved and combined with multi-grid method for accelerating the convergence speed, and a finite analytic + multi-grid method for calculating electric field distribution has been developed.Numerical simulation of gas flow field Through mathematical deducing, the control equation set and for describing the time dependent compressible viscous flow have been given at the calculating plane. The discrete scheme of those control equations have also been deduced by the finite volume method and combined with multi-grid method which forms a Finite volume + Multi-grid Method for calculating the time dependent compressible viscous flow.For the sack of solving the hard problems encountered in the numerical simulation of the velocity-pressure gradient coupling problem, the interlock grid technique and the linear distribute iteration method have been adopted. So that those hard problems have been well solved.Applying this numerical simulation method, the 550kV circuit breaker was taken as numerical calculation example and the gas blast flow during breaking process of 260mm open stroke has been simulated at each 1mm calculating step. The simulation results have been compared with the results calculated by commercial software FLUENT which show that the numerical simulation method given by this thesis is correct.On the basis of the research results, the numerical simulation of dielectric recovery properties of 550kV circuit breaker under non-load breaking and short circuit breaking have been carried out and discussed. The results show that the numerical method for dielectric recovery property simulation given by this thesis is feasible.
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